HTML Unleashed PRE: Strategies for Indexing and Search Engines

Frames

One of the features of HTML 4.0 deserves special attention with
respect to search engines accessibility. About half of the major
search engines cannot penetrate framed sites. For them, the root page
of a frameset is all that can be viewed and indexed on the site, and
all the framed pages below the root are missed.

The best solution for this problem (as well as for the problem of
frames accessibility to people with disabilities; see Chapter 42,
"Creating
Widely Accessible Web Pages") is the NOFRAMES
element. It should be placed within the FRAMESET
element, usually before the first FRAME tag, and may
contain any text, links, or other material. This is what
search engines will see on the page and reflect in the database,
while frame-capable browsers will ignore anything within a
NOFRAMES element.

To make the rest of your content accessible, you should provide
links to the framed pages from within the NOFRAMES element.
Remember that you're doing this not only for spiders, but also for the users
of non-graphical browsers, so accompany the links with proper
descriptions. Usually, one of the frames contains a navigation bar
with links to all other pages, so in the NOFRAMES element it
may be enough to link to this document only.

For framed pages to be usable in the absence of frame context, remember
to give them their own TITLE elements (this will improve
their ranking in search engines as well).